Vehicle tire manufacture most commonly takes place in stages. In an early stage of the manufacturing procedure, there is formed a belt and tread package. This package comprises a plurality of strips (belts) of elastomeric material and/or other similar components that are formed into a toriodal shape by winding the strips about the outer circumference of a rotating belt and tread drum, with bonding of the strips into the belt and tread package. Commonly, the belt and tread package also has included therein metal bead rings that ultimately aid in defining the rim diameter and circumference of the tire. The package thus formed is nonexpandable in diameter. After the package has been formed on the belt and tread drum, the drum most commonly is collapsed in outer circumference to allow removal of the formed package from the drum. Thereafter, the drum is expanded to its desired outer circumference for the forming of a subsequent belt and tread package thereon. The belt and tread package which has been removed from the drum is conveyed to a further stage in the procedure where it is married to a tire carcass and undergoes other stages of manufacture.
In the vehicle tire manufacturing industry, there are many belt and tread machines which have been in use for several years. These machines generally include a core which is cantilevered on a rotatable shaft that is connected at one of its ends to a drive mechanism. The core generally includes some form of outer generally cylindrical shell whose diameter (hence its circumference) is changeable within limits to permit the shell to be collapsed in diameter for removal of a formed belt and tread package therefrom. A substantial number of these shells have no provisions for selecting different overall diameters of the drum and therefore are limited to the manufacture of a belt and tread package for a single size tire. Some of these existing shells have some capacity for changing the overall diameter of the drum, but are most commonly very limited in their range of possible diameter change. It is desired that these existing belt and tread drums be retrofitted with means for enhancing the range of diameters possible to be obtained with the drum, hence make the drum useful in the manufacture of a greater range of tire sizes. It is also desired that the changeover between diameters be made more efficient and friendly to the equipment operator. Attaining these desired results is greatly impeded because of certain of the limitations imposed upon the permissible modifications that can be accepted in designing a retrofit shell for these drums. Specifically, commonly the core of these existing machines is very large in diameter, leaving relatively little annular space in which to make modifications to the shell of the drum. Further, the machines are designed to provide ancillary services, pressurized air for example, to the shell which currently is employed with the machine and any retrofitted shell preferably must be adapted to the location and value of such ancillary services.
It is an object of the present invention to provide a belt and tread drum which includes enhanced expansion/retraction capabilities.
It is another object to provide a retrofit shell for an existing core of a belt and tread drum.